Axial flow turbine structure

ABSTRACT

An axial flow gas turbine having inner and outer casings, the inner casing being supported within the outer casing by horizontal keying members therebetween. Arrays of stationary integral vane segments and adjacent arcuate blade ring segments are supported inwardly from and interlocked with the inner casing by arcuate segmented support members. The arcuate segmented support members are each fixedly attached at their centermost point to the inner casing. This arrangement permits thermal expansion between mating members with respect to each other. The employment of individually locked stationary integral vane segments and arcuate blade ring segments provide an arrangement where blade path leakage harmonics are limited to the number of such segments in each of their respective planes across the turbine, thus eliminating the deleterious effects created by even harmonics of two stationary half blade segment structures.

United States- Patent [1 1 Scalzo [45 Oct. 15, 1974 1 AXIAL FLOW-TURBXNE STRUCTURE [21] Appl. No.: 394,599

[52] [1.5. Cl 415/136, 415/138, 415/178 [51] Int. Cl. F0ld 25/26, FOld 5/08 [58] Field of Search 415/134, 136,138,115,

[56] References Cited UNITED STATES PATENTS 2,919,891 l/1960 Oliver 415/136 Primary ExaminerHenry F. Raduazo Attorney, Agent, or Firm-D. N. Halgren [57] ABSTRACT An axial flow gas turbine having inner and outer casings, the inner casing being supported within the outer casing by horizontal keying members therebetween.

Arrays of stationary integral vane segments and adjacent arcuate blade ring segments are supported inwardly from and interlocked with the inner casing by arcuate segmented support members. The arcuate segmented support members are each fixedly attached at their centermost point to the inner casing. This arrangement permits thermal expansion between mating members with respect to each other. The employment of individually locked stationary integral vane segments and arcuate blade ring segments provide an arrangement where blade path leakage harmonics are limited to the number of such segments in each of their respective planes across the turbine, thus eliminating the deleterious effects created by even harmonics of two stationary half blade segment structures.

4 Claims, 5 Drawing Figures 1 AXIAL FLOW TURBINE STRUCTURE BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to axial flow turbine structures, and more particularly to such turbines structures employing a hot motive fluid.

2. Description of the Prior Art 7 Turbines operated with hot motive gases, for example, gas turbines, require cooling fluids, such as air, to control temperatures of stationary components as well as rotating components. Turbines of this type are usually provided with outer casings divided in a horizontal plane with upper and lower halves bolted together, for ease of assembly and service. Also, pressurized cooling air or other suitable fluid is directed through the outer easing into the annular plenum chamber or space between the outer casings and the outer diaphragm shrouds and then through the stationary turbine blades. It has been found that undesirable leakage of cooling air from the annular space into the motive fluid flow path occurs in operation. This leakage is most pronounced at the horizontal joint of the turbine diaphragms and at the juncture of adjacent shroud portions of stationary blade segments that comprise the diaphragm. An analysis of the harmonic vibration of the above described leakage pulses indicates that even harmonics of the turbine running speed are produced which in some instances results in blade excitation leading to failure.

Assuming that leakage of cooling air past the horizontal joint can be eliminated, an excitation pattern can still persist as a result of changes in stationary blade gauging or pitch, i.e., spacing between adjacent blades through which the motive fluid flows. Changes in gauging results when the outer shrouds of the stationary blade diaphragms expand relative to the casing with consequent uneven shifting in circumferential direction of the stationary blades. The amount of gauging change is proportional to the number of blades in the integral structure which is maximum for a two-half diaphragm system.

In addition to the above, shroud restraints in existing 180 divided diaphragms can develop excessive thermal stresses of a damaging nature during transient operating temperature cycles.

One of the primary objects of this invention is to provide a turbine structure having inner and outer casings in which damaging leakage of cooling air between adjacent stationary blade shroud segments is eliminated.

A further object of this invention is to provide an improved turbine structure in which the inner casing is freely supported-in a horizontal relationship with respect to the outer casing.

A still further object of the invention is to provide an improved turbine structure in which the inner casing is maintained in vertical alignment with respect to the outer casing.

Yet another object of the invention is to provide an improved stationary blade diaphragm and inner casing structure for a turbine wherein the blades are formed in a manner to conduct cooling air flow, wherein leakage of cooling air therepast is minimized, and in which the blades are free to expand relative to their support ing members and to the casing.

A still further object of the invention is to provide an improved mounting arrangement for an annular row of hollow air cooled stationary blade segments and axially adjacent blade ring segments.

SUMMARY OF THE INVENTION Generally, there is provided an axial flow gas turbine having an annular row of stationary blades, an annular row of rotatable blades carried by a rotor and cooperatively associated with the stationary blades, and an annular multiple member inner casing emcompassing the stationary blades and the rotatable blades.

There is further provided an annular outer casing encompassing the inner casing and jointly therewith providing a common plenum chamber or space of annular shape. The inner casing is supported and maintained horizontally within the outer casing by flange-like keys disposed between the two casings. The keys extend horizontally outwardly off the inner casing wall and engage a key receiving member within the inner walls of the outer casing. The inner casing is held in vertical alignment by a plurality of pins disposed in the longitudinally vertical plane between the two casings.

The inner casing engages arcuate support segment. These arcuate support segments and easing slidably mate because of track and channel interlock arrangements on the inner side of the inner casing and the support segments. The radially inner edges of the arcuate supportsegments mate with the stationary vane segments and with the arcuate blade ring segments. The arcuate support segments are locked or fixedly attached only at their midpoint, to the inner casing. This permits thermal expansion and also contraction within the support members with respect to the inner casing. The slidable support arrangement also permits dimensional changes in the supported vane and arcuate blade ring segments with respect to one another.

BRIEF DESCRIPTION OF THE DRAWINGS The objects and advantages of this invention will become more apparent from reading the following detailed description in connection with the accompanying drawings, in which:

FIG. I is an axial sectional view of a portion of a gas turbine incorporating the invention;

FIG. 2 is an axial sectional view of the locking arrangement for the support segments; FIG. 3 is a view taken along the lines Ill-III of FIG.

FIG. 4 is a view of the locking arrangement for the stationary blade shroud segments; and

FIG. 5 is a view taken along the lines V-V of FIG. 4.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in detail, particularly in FIG. 1, there is shown an axial flow gas turbine 10. Only a portion of the upper half is shown since the lower half is identical to the upper half. The turbine 10 comprises an outer casing 12 of generally tubular or annular shape, multiple inner casings 14 of annular shape encompassed by the outer casing 12, and a rotor 16 rotatably supported within the multiple inner casings 14 in any suitable manner, not shown, and having a plurality, two in this example, of annular rows or arrays of blades 18 and 20.

Cooperatively associated with the rotor blades 18 and 20, to form two stages, for this example, for motive fluid expansion, is an equal number of blade diaphragms or annular rows of stationary blades 22 and 24, supported within the inner casing 14. An annular grouping of stationary blades 22 or 24, comprise an integral arcuate vane segment 23.

The rotor blades 18 and 20, are substantially similar to each other except for a gradual increase in height from left to right, and are of the unshrouded type with a radially outwardly extending vane portion 26 and a root portion 28 suitably secured to the rotor 16.

In a similar manner, the stationary blades 22 and 24, are substantially similar to each other but gradually increase in height from left to right, and are provided with a radially inwardly extending vane portion 30, a base portion 32, and an outer shroud portion 34. The outer shroud portion 34 comprises a portion of the track and channel arrangement for supporting the integral vane segments 23.

As is well known in the art, hot motive fluid, such as pressurized combustion gas, generated in a suitable combustion chamber, not shown, is directed through the first row of stationary vanes 22 past the rotor blades 18 and 20, in the direction indicated by the arrow 35a, with resulting expansion of the motive fluid to rotate the rotor 16 about its longitudinal axis, and thence directed through a suitable outlet, not shown, located at the furthermost downstream end of the turbine 10.

In accordance with the invention, as shown in FIG. 1, the inner casing 14 is supported within the outer casing 12 by keying members 36 disposed in the horizontal plane. Each keying member 36, is slidably engaged with a keyway 38, or key member shoulder-like support. The keying members 36 provide horizontal support for each member of the multiple inner casing 14. Viewing FIG. 1, now in a vertical plane, there is shown a plurality of vertically disposed pins 40, which are located on the longitudinally vertical plane of the turbine 10. The pins 40 are disposed on both the upper and the lower halves of the turbine 10. The pins 40 transmit torque from the stationary blades, 22 and 24, only two shown, to the outer casing 12. The vertically disposed pins 40 also maintain transverse alignment of each member of the multiple inner casing 14.

An annular plenum chamber 42 is disposed along the radially outward side of the multiple inner casing 14. Pressurized cooling air is introduced into the stationary blades 22 and 24, and the like, from the plenum chamber 42 through passageways, not shown, in the multiple inner casing 14. A spring loaded arcuately segmented face seal 43 provides restriction of gas leakage between the motive fluid flow path and the plenum chamber 42.

Arcuate isolation segments 44 are disposed on the radially inner side of each member of the multiple inner casing 14. The arcuate isolation segments 44 provide the support for the outer shroud portions 34 of the-stationary arcuate vane segments 23 that comprise the annular arrays of stationary blades 22 and 24, and the like. The arcuate isolation segments 44 slidably mate with grooves 45 in a track and channel arrangement 51 to support the stationary vane segments 23 comprised of the blades 22 and 24. The isolation segments 44 also i tially adjacent arcuate blade ring segments 46. This controls leakage of cooling air therepast. Furthermore, the chances of undesirable even harmonics, which could damage the rotating blades 18 and 20, and the like, is eliminated. The outer shroud members 34 and the arcuate blade ring segments 46 are slidably disposed on the radially inner edge of the arcuate isolation segments 44. The upstream side of the arcuate blade ring segments 46 are slidably and supportively disposed in a track like shoulder and flange arrangement 47 with the downstream edge of adjacent upstream shroud members 34. The slidable track and channel interlock and support arrangement 51 between the inner casing 14 and'the arcuate isolation segments 44 permit circumferential expansion of respective members in relation to one another, without buildup of stresses therein.

A similar track and channel interlock arrangement 49 is disposed between the arcuate isolation segments 44 and their respective supported members, which are the arcuate shroud members 34 and the arcuate blade ring segments 46. The arcuate isolation segments 44 isolate the members of the multiple inner casing 14 from the hotter parts of the turbine, that is, the vane segments 23 and the arcuate blade ring segments 46, to prevent distortion within those members of the inner casing 14. Excessive distortion of the inner casing 14 would cause blade rubs and would reduce the performance of the turbine 10.

FIG. 2 shows an embodiment ofa locking system for the arcuate isolation segments 44. Bolts 48,- in registration with the members of the multiple inner casing 14, anchor each isolation segment 44 in place with respect to each member of the multiple inner casing 14. Retaining member 50 and 53, bolted to each member of the multiple inner casing 14, retain the arcuate isolation segments 44 against the multiple inner casing 14. Retaining member 50 also locks the arcuate blade ring segments 46 with respect to each member of multiple inner casing 14, as shown in FIG. 3. Contiguous surfaces of adjacent arcuate isolation segments 44, of adjacent shroud portions 34, and of adjacent arcuate blade ring segments 46, have male-female sealing strips 52 that provide a sealing arrangement between adjacent members. This reduces leakage of cooling air from the plenum chamber 42 into the hot motive fluid flow path. The use of integral arcuate stationary vane segments 23 permits leakage harmonics that will not be dangerous to the turbine 10, if in fact any leakage does occur.

The vane segments 23 are locked with respect to the multiple inner casing 14 by an arrangement shown in FIGS. 4 and 5. Each vane segment 23 is fixedly attached from only a center point on its curvature to the inner casing 14. This reduces the deleterious effects of thermal expansion between mating members. A vane segment lock pin 54 is disposed through each member of the multiple inner casing 14. The lock pin 54 is pro- .vided with machined flats 55 that registers with mating slots 60 in the radially outer portion of the shroud member 34. The pin 54 extends through a portion of the isolation segment 44 to register with each vane segment 23. A lock pin retainer 56 maintains the lock pin 54 in registration with the member of the multiple inner casing14. The lock pin retainer 56 is secured to the member of the multiple inner casing 14 by bolts 57. The flats 55 on the lock pin 54 extending into the slots 53 allows rotation of the lock pin 54 to orient the flats with the slots 60 to control contact stress.

An annular array of the individually locked vane segments 23 provide a unique leakage harmonic equal to the number of vane segments 23. This eliminates the troublesome family of even harmonics associated with the horizontal type joint leakage. The male-female seal strips 52 between adjacent blade rings 46, between adjacent isolation segments 44, and between adjacent vane segments 23, help control the leakage flow.

It will be seen that the thermal expansion of the components during operation is readily accommodated while still maintaining sealing against leakage of cooling fluid from the plenum chamber 42 into the, blade region, while also minimizing of thermal stresses that would otherwise occur.

Though the invention has been shown generally in one embodiment, it will be obvious hereinafter to those skilled in the art that it is not so intended or limited, and that the invention is susceptible of alterations without departing from the spirit and scope thereof.

I claim as my invention:

1. An axial flow turbine comprising:

an outer generally cylindrical casing,

a generally coaxial inner casing, said outer and said inner casings generally defining a plenum chamber therebetween,

an annular array of stationary blades disposed within said inner casing having an outer shroud portion,

a rotor having an array of rotatable blades on its periphery, said rotatable blades being coaxial and adjacent said stationary blades,

an array of arcuate blade ring segments disposed radially outwardly of said rotatable blades,

said array of stationary blades comprising arcuate integral vane segments thereof,

said stationary blades being supported from said inner casing by arcuate support segments, said arcuate support segments and said inner casing having a track and channel interlock arrangement therebetween, said arcuate support segments and 6 said outer shroud portion of said stationary integral vane segments having a track and channel interlock arrangement therebetween, each arcuate support segment being fixedly attached at one point on its periphery to the inner casing to permit circumferential thermal expansion of said segments,

said array of arcuate blade ring segments being supported radially outwardly of said rotatable blades by arcuate support segments having track and channel interlock arrangements with the inner casing and also having a track and channel interlocking support arrangement between an edge of each of said ring segments and the downstream edge of adjacent upstream stationary integral vane segments,

said inner casing being supported within said outer casing by generally horizontal keying members, said keying members being received in keyways within said outer casing,

and at least two generally vertically disposed pins disposed between each inner casing member and said outer casing providing vertical alignment of said inner casing member with respect to said turbine.

2. An axial flow turbine arrangement as recited in claim 1 wherein said support segments for said ring segments are fixedly attached at one point to said casing to permit circumferentially directed thermal expansion of said support segments with respect to its adjacent components.

3. An axial flow turbine arrangement as recited in claim 1, wherein a biased arcuate member provides sealing means between the plenum chamber and the axial hot fluid flow path.

4. An axial flow turbine arrangement as recited in claim 1, wherein said turbine comprises a plurality of annular arrays of stationary blades and a plurality of rotatable blades, each annular array of stationary blades being supported by said arcuate support arrangement. 

1. An axial flow turbine comprising: an outer generally cylindrical casing, a generally coaxial inner casing, said outer and said inner casings generally defining a plenum chamber therebetween, an annular array of stationary blades disposed within said inner casing having an outer shroud portion, a rotor having an array of rotatable blades on its periphery, said rotatable blades being coaxial and adjacent said stationary blades, an array of arcuate blade ring segments disposed radially outwardly of said rotatable blades, said array of stationary blades comprising arcuate integral vane segments thereof, said stationary blades being supported from said inner casing by arcuate support segments, said arcuate support segments and said inner casing having a track and channel interlock arrangement therebetween, said arcuate support segments and said outer shroud portion of said stationary integral vane segments having a track and channel interlock arrangement therebetween, each arcuate support segment being fixedly attached at one point on its periphery to the inner casing to permit circumferential thermal expansion of said segments, said array of arcuate blade ring segments being supported radially outwardly of said rotatable blades by arcuate support segments having track and channel interlock arrangements with the inner casing and also having a track and channel interlocking support arrangement between an edge of each of said ring segments and the downstream edge of adjacent upstream stationary integral vane segments, said inner casing being supported within said outer casing by generally horizontal keying members, said keying members being received in keyways within said outer casing, and at least two generally vertically disposed pins disposed between each inner casing member and said outer casing providing vertical alignment of said inner casing member with respect to said turbine.
 2. An axial flow turbine arrangement as recited in claim 1 wherein said support segments for said ring segments are fixedly attached at one point to said casing to permit circumferentially directed thermal expansion of said support segments with respect to its adjacent components.
 3. An axial flow turbine arrangement as recited in claim 1, wherein a biased arcuate member provides sealing means between the plenum chamber and the axial hot fluid flow path.
 4. An axial flow turbine arrangement as recited in claim 1, wherein said turbine comprises a plurality of annular arrays of stationary blades and a plurality of rotatable blades, each annular array of stationary blades being supported by said arcuate support arrangement. 